Haptic excitations/vibrations are employed in mobile devices such as smartphone and tablets for a variety of applications. A first application is to cause a mobile device which is set to a “silent” mode to vibrate in response to receiving a telephone call, message or other similar notification. A user carrying the mobile device in a pocket may then become aware of the incoming call, message and so forth, even though no audible sound is produced by the mobile device.
Another application of haptics is to provide user feedback relating to input. For example, when a user has touched the correct location of a touchscreen to actuate a button, the mobile device may be caused to vibrate for a short period to provide tactile feedback confirming the button actuation. Such feedback can augment audible button “click” sounds, or replace them for quiet or silent operation of the phone.
Conventionally, mobile devices use rotary mass or linear resonant actuators in order to generate such haptic excitations/vibrations. However, such devices can be bulky and may consume relatively large amounts of energy, reducing the length of time that a mobile device can operate on battery power.
Conventional vibration of mobile devices and touchscreens is non-localised. With the aim of improving user experience, there has been interest in trying to localise excitations/vibrations to particular locations of a touchscreen.
For example, US 2015/0277565 A1 describes a touch sensitive device comprising a panel capable of supporting bending waves, a user-accessible touch sensitive screen on or forming part of a face of the panel, the touch sensitive screen having a plurality of different sensing areas, a plurality of vibration exciters coupled to the panel to apply bending waves to the panel to provide tactile feedback at the plurality of sensing areas in response to the user touching a sensing area, and signal processing means arranged to apply signals to the vibration exciters so as to steer bending waves applied to the panel by the plurality of vibration exciters whereby the amplitude of the applied bending waves is maximised at the sensing area touched by the user and reduced or minimised at each other sensing area.